ForceTile is a novel tabletop tangible interface that detects force distribution, position, rotation, and ID. In previous optical force sensors, an elastic body and cameras are fixed together. With this system, users can freely move tile-shaped elastic bodies on the tabletop display. First the system detects the position, rotation, and ID of each interface on the tabletop by position markers attached on bottom surfaces of the tiles.

Then it calculates the force vectors on each interface by using cameras and IR transmitters underneath the table. The interface does not disturb the back projection because it uses transparent heat-insulating material as the force markers and a special tabletop screen. Users control projected images with their fingers in various ways, such as moving, pushing, pinching.

Enhanced Life
Users can interact with displayed images on the tabletop screen by using not only interface positions (placing, moving, and connecting), but also finger input such (pushing, twisting, and pinching). The appearance of the interface changes interactively in response to user input.

Goals
The overall goal of ForceTile is to increase the interactivity of tabletop tangible interfaces without installing electronic devices on them. More concretely, the goal is to develop an interface that uses a vision-based approach to detect force distribution on its surface as well as the force's position, rotation, and ID.

Innovations
The core innovation is the system's ability to detect the position, ID, and force distributions on the tile. Cameras inside the system capture ID markers to detect positions and IDs. They also track the movement of markers embedded inside the tiles to derive the magnitude and direction of forces applied on the tile's surface.

Vision
ForceTile could integrate several functions of previous interfaces simultaneously such as touch panels, pointing devices (mouse, trackpad), tangible physical interfaces, and small-sized screens. These interactions enable various tabletop applications for games, education, and media art. In the near future, ForceTile will be adapted to other types of displays.